Hara took the concept of "a 1,000 men unit can affect the whole battlefield" to the extreme with Raku'a Kan and Hakuokoku. Both against Renpa's and Gokei's armies, they performed some feat(s) which were decisive in tipping the balance in Han's favour. It's just really unclear what, especially against the Renpa army which was so stacked. Against Gokei, it'd be way easier to come up with something. But I doubt Hara will ever expand on this stuff lol.
Obviously it's clear that at that time they were above the average 1,000 men commander lol. And I'd be interested in getting something on the Han commander in chief back. The bloke who nonetheless would have shouldered the biggest weight in those battles. Because even with Raku'a Kan's and Hakuokoku's exploits in the field, this guy must have been a beast.
Then those two rapidly advanced through the ranks, even becoming the most discussed generals in China at one time. They repelled the invaders but here the likes of Renpa and Gokei aren't mentioned. Current Raku'a Kan (who is = to the Raku'a Kan of back then) clearly ranks as a strong Great General but one who will still decisively get defeated by Tou the first time he goes to battle again.
So yeah. Especially Raku'a Kan is great, but not legendary.